OBJECTIVES: To estimate unexplained osmolal gaps (UEOG) during ethanol ingestions after accounting for measured ethanol concentrations and to explore the causes of observed discrepancies. DESIGN AND SPECIMENS: A random convenience sample of serum specimens with a request to perform osmometry for the detection of alcohols was studied. MAIN OUTCOME MEASURES: Serum concentrations of sodium, glucose, urea nitrogen, ethanol, osmolality, and ethanol were measured by two analytic methods to determine calculated osmolalities and osmolal gaps using two commonly used formulas. RESULTS: In 79 serum specimens submitted for osmometry, mean ethanol concentrations were 199 +/- 154 (SD) mg/dL; 15 specimens had no detectable ethanol. After regression of the calculated ethanol concentrations and the measured ethanol concentrations, the Dorwart and Chalmers formula showed a large constant bias of 45.217 +/- 6.414 (SE) mOsm/kg in predicting measured ethanol concentrations. The Smithline and Gardner formula was similarly as precise (r = .9786), but had a much smaller bias of -3.929 +/- 6.623 (SE) mOsm/kg. Actual mean differences between measured and calculated osmolalities (including ethanol osmols) gave an estimate of UEOG seen during ethanol ingestions. Using the less biased formula, the mean UEOG was 1.4 +/- 8.5 mOsm/kg, giving a 95% upper limit of the reference range of 18 mOsm/kg in this population with ethanol ingestions. Three significant outliers were identified and their UEOG could be explained by the presence of mannitol, isopropanol, or possibly a change in the assumed value for fractional water, normally a constant in these formulas for calculated osmolality. Other specific causes of osmolal gap and UEOG are discussed. CONCLUSION: The potential range of osmolal gaps seen during ethanol ingestions after accounting for ethanol is demonstrated to be greater than in previous studies, which have included a lower proportion of ethanol-intoxicated subjects in their study sample.
OBJECTIVES: To estimate unexplained osmolal gaps (UEOG) during ethanol ingestions after accounting for measured ethanol concentrations and to explore the causes of observed discrepancies. DESIGN AND SPECIMENS: A random convenience sample of serum specimens with a request to perform osmometry for the detection of alcohols was studied. MAIN OUTCOME MEASURES: Serum concentrations of sodium, glucose, ureanitrogen, ethanol, osmolality, and ethanol were measured by two analytic methods to determine calculated osmolalities and osmolal gaps using two commonly used formulas. RESULTS: In 79 serum specimens submitted for osmometry, mean ethanol concentrations were 199 +/- 154 (SD) mg/dL; 15 specimens had no detectable ethanol. After regression of the calculated ethanol concentrations and the measured ethanol concentrations, the Dorwart and Chalmers formula showed a large constant bias of 45.217 +/- 6.414 (SE) mOsm/kg in predicting measured ethanol concentrations. The Smithline and Gardner formula was similarly as precise (r = .9786), but had a much smaller bias of -3.929 +/- 6.623 (SE) mOsm/kg. Actual mean differences between measured and calculated osmolalities (including ethanol osmols) gave an estimate of UEOG seen during ethanol ingestions. Using the less biased formula, the mean UEOG was 1.4 +/- 8.5 mOsm/kg, giving a 95% upper limit of the reference range of 18 mOsm/kg in this population with ethanol ingestions. Three significant outliers were identified and their UEOG could be explained by the presence of mannitol, isopropanol, or possibly a change in the assumed value for fractional water, normally a constant in these formulas for calculated osmolality. Other specific causes of osmolal gap and UEOG are discussed. CONCLUSION: The potential range of osmolal gaps seen during ethanol ingestions after accounting for ethanol is demonstrated to be greater than in previous studies, which have included a lower proportion of ethanol-intoxicated subjects in their study sample.
Authors: Larry D Lynd; Kathryn J Richardson; Roy A Purssell; Riyad B Abu-Laban; Jeffery R Brubacher; Katherine J Lepik; Marco L A Sivilotti Journal: BMC Emerg Med Date: 2008-04-28